Chains have been conventionally used to transmit rotation among plural shafts. For example, a chain is wound around an input shaft inputted with driving force from an engine and an output shaft transmitted with driving force distributed from the input shaft in accordance with a driving condition of a vehicle. Generally, lubricating oil is used to components such as the chain, the input shaft and output shaft, in order to reduce abrasion or heating-up caused by friction between such components. However, it is difficult to supply lubricating oil all over the components to be lubricated. Further, the lubricating oil may be occasionally supplied to each component at an amount exceeding an adequate amount, which is not preferable.
As one of the examples, a transfer to distribute driving force of an input shaft to output shafts in relation to front wheels and rear wheels, is mounted to a four-wheel drive car (4WD). The transfer is provided with a case in which lubricating oil is accumulated so as to protect a chain, the input shaft, the output shafts and so on, from being worn out or from heating up due to rotations thereof. The lubricating oil is accumulated at a lower space of the case, and a lower portion of the chain is soaked thereinto. The chain lifts the lubricating oil upwards when rotating, and as a consequence, the chain, the input and the output shafts wound around by the chain, and so on are lubricated. The lower space of the case is divided into two chambers from the bottom portion of the case to the intermediate portion thereof by a plate member (separator). The separator is arranged so as to be in parallel with a plane of the rotation of the chain. One of the chambers of the lower space includes a chain and the other chamber includes a strainer having an inlet communicating with a pump adapted to suck up lubricating oil. The strainer filters out the lubricating oil so as to separate scraps such as scrap metals from the lubricating oil. The lubricating oil is circulated by the pump through the strainer and lubricates each component that is not lubricated by the lubricating oil lifted by the chain. The separator divides the lower space of the case into the two chambers (chain-side chamber and strainer-side chamber) so that each chamber could store therein a different amount of lubricating oil, i.e., each chamber could have a different lubricating oil surface level. When the lubricating oil surface level of the chain-side chamber is appropriate, the chain is soaked in the lubricating oil. When the amount of lubricating oil in the chain-side chamber is large and the lubricating oil surface level of the chain-side lubricating oil is too high, resistance (stirring resistance) relative to the rotation of the chain is increased and the transmitting efficiency of the rotation is reduced. Meanwhile, it is necessary to keep a lubricating oil surface level, or an amount of lubricating oil, of the strainer-side portion at an appropriate degree at which the inlet of the strainer related to sucking up the lubricating oil is sufficiently soaked in the lubricating oil. Should the lubricating oil surface level of the strainer-side portion be low, the inlet thereof may be easily exposed out of the lubricating oil. In such circumstances, the pump may suck up the air as well as the lubricating oil.
The present invention has been made in view of the above circumstances and provides a chain-type driving force transmitting apparatus which adjusts amounts of lubricating oil in two chambers of a lower space of a case thereof.